The present invention relates to a unit and method for transferring cigarette portions.
Between a cigarette manufacturing machine and a filter assembly machine, a transfer unit is normally located to transfer to an input drum of the filter assembly machine the cigarette portions fed longitudinally in a first straight horizontal direction along a forming beam of the manufacturing machine.
Such units are known to comprise a first conveyor having a number of pickup heads, each of which travels along a first annular path about a first axis perpendicular to the first direction, and comprises a first seat for removing a cigarette portion off the forming beam and which is maintained parallel to the first direction as the head is fed along the first annular path.
The transfer unit also comprises a second conveyor rotating about a second axis parallel to the first direction and having a number of second seats parallel to and equally spaced about the second axis to receive the cigarette portions from respective first seats on the first conveyor at a transfer station.
The transfer unit described above is suitable for transferring cigarette portions from a single-rod manufacturing machinexe2x80x94i.e. a machine on which a single succession of cigarette portions is fed along the forming beamxe2x80x94to the input drum of a filter assembly machine.
The second conveyor of the above unit is normally a drum, the spacing of the second seats on the outer periphery of which is determined by the length of each filter paper, and therefore by the cigarette diameter and the design characteristics of the filter assembly machine, so that, for a given spacing of the second seats, the tangential speed of the second seats and, therefore, the diameter and angular rotation speed of the drum are directly proportional to the output (number of cigarettes per minute) required of the line defined by the manufacturing machine and the filter assembly machine as a whole.
The angular rotation speed of the first conveyor about the first axis is constant and depends on the ratio between the output required and the number of pickup heads on the first conveyor.
Each pickup head is normally fitted in rotary manner to an arm in turn fitted in rotary manner to the conveyor, and the constant-speed rotations of the conveyor and arms are coordinated so that each pickup head is fed along an elliptical annular first path.
The reason the pickup heads are fed along an elliptical as opposed to a circular path lies in the cigarette portions normally being fed longitudinally along the forming beam of the manufacturing machine at a much faster speed than that at which the cigarette portions are fed transversely by the second seats on the drum. An elliptical annular path, in fact, enables the pickup heads to be advanced at variable speed and to transfer the cigarette portions to the second seats at a different (lower) speed from that at which the cigarette portions are removed from the forming beam. More specifically, at best, the transfer speed should be approximately equal to but no less than the tangential speed of the second seats on the drum, and the pickup speed should be approximately equal to but no less than the speed at which the cigarette portions are fed longitudinally along the forming beam.
For a given output rate, two requirements must be borne in mind when designing the first conveyor and relative arms: one is to achieve as compact a conveyor as possible, and the other to achieve the best pickup and transfer speeds as explained above. Since the design of the first conveyor and relative arms, however, also depends on both the number of pickup heads and the required pickup and transfer speeds, it is often difficult if not impossible to meet both requirements satisfactorily within the above design limitations.
The problem is further compounded in the case of transfer units operating with so-called dual-rod manufacturing and filter assembly machines.
A transfer unit for dual-rod lines is described, for example, in Patent GB 2,259,289. In this case, the transfer unit is associated with a forming beam along which two parallel successions of cigarette portions are fed, and comprises a first conveyor having a number of pickup heads traveling along an elliptical path and in turn having two parallel first seats. The unit also comprises a second conveyor defined by a drum, which rotates at constant angular speed and has a first group of second seats formed in the outer skirt of the drum, and a second group of second seats formed on the ends of respective arms movable with respect to the drum, and alternating with the second seats in the first group. The second seats in the second group are movable between a conveying position adjacent to the outer skirt of the drum, and a receiving position to receive the cigarette portions from the pickup heads and in which they project with respect to the skirt.
In a transfer unit of this sort, the above design limitations result in a much faster speed of the first seats with respect to the second seats at the transfer station. Combined with the fact that the cigarette portions are severely decelerated axially during transfer, the difference in speed between the first and second seats results in transverse impact of the cigarette portions as they are transferred from the first to the second seats, and in tobacco fallout from the ends of the cigarette portions.
The problem is further compounded as regards the seconds seats in the first group, by the peripheral speed of these being slower than the second seats in the second group in the receiving position.
Another transfer unit for dual-rod lines is described in U.S. Pat. No. 5,267,577. In this case, the unit comprises a second conveyor defined by a cage roller housing a drum; the second seats in the first group are locatd on the drum, and the second seats in the second group on the cage roller; and the ratio of the drum and cage roller rotation speeds is inversely proportional to the ratio of the respective radii, so that the peripheral speed of the first group of second seats is equal to the peripheral speed of the second group of second seats.
A transfer unit of this sort has the advantage of the second seats in the first and second groups traveling at the same peripheral speed at the transfer station. On the other hand, the design limitations referred to in connection with single-rod lines are even more stringent in this case, by the elliptical shape of the annular path having to be so designed as to prevent the trajectories of the first seats on the first conveyor and the second seats on the second conveyor from intersecting each other.
In this case, too, therefore, the above design limitations result in a much faster speed of the first seats with respect to the second seats at the transfer station. And as stated previously, combined with the fact that the cigarette portions are severely decelerated axially during transfer, the difference in speed between the first and second seats results in transverse impact of the cigarette portions as they are transferred from the first to the second seats, and in tobacco fallout from the ends of the cigarette portions.
It is an object of the present invention to provide a unit for transferring cigarette portions, designed to eliminate the drawbacks of the known state of the art.
According to the present invention, there is provided a unit for transferring cigarette portions from a manufacturing machine to a filter assembly machine; the unit comprising a first conveyor having a number of first seats movable along a first annular path about a first axis to pick up respective cigarette portions at a given pickup point along the first path; and a second conveyor having at least one number of second seats movable along a respective second annular path about a second axis perpendicular to the first axis; each said second seat receiving a cigarette portion from a said first seat at a transfer point along said first path; and the unit being characterized in that, for at least one said number of second seats, each second seat is located at the end of an arm which is movable to correct the speed of the second seats to substantially reach or approximate the speed of the first seats at said transfer point.
The present invention also relates to a method of transferring cigarette portions.
According to the present invention, there is provided a method of transferring cigarette portions from a manufacturing machine to a filter assembly machine by means of a transfer unit comprising a first conveyor having a number of first seats movable along a first annular path about a first axis to pick up respective cigarette portions at a given pickup point along the first path, and a second conveyor having at least one number of second seats movable along a respective second annular path about a second axis perpendicular to the first axis; the method providing for feeding each said second seat about said second axis, and transferring a cigarette portion from a first seat to a second seat at a transfer point along said first path; and the method being characterized by correcting, for at least one said number of second seats, the speed of the second seats so as to substantially reach or approximate the speed of the first seats at the transfer point.